Facebook has just made it easier, faster and more effective for mobile advertisers to reach, remarket and reengage their customer bases.

In its continued focus on solving challenges for the mobile industry, Facebook recently released a new custom audience solution designed specifically for mobile app developers: app user IDs. To date custom audiences have enabled marketers to take their CRM information (specifically email addresses, phone numbers or Facebook user IDs) and match them with Facebook profiles containing this same information. The targetable audience created through this process has proven to be a lucrative strategy for marketers from retail to gaming, with results like increasing the ROI of campaigns by 5X and driving 100% same-day ROI multiple days in a row.

App user IDs extend the benefits of custom audience targeting to mobile in order to solve some of the unique challenges marketers face when remarketing and reengaging their app user bases. In particular, the fact that many mobile apps can be installed and used without requiring a user to register or provide personal information at all.

Which brings us to the first benefit of custom audience targeting with app user IDs:

No registration or Facebook Login required

Many mobile apps do not require users to register (with their email address, phone number or through Facebook Connect) in order to use them. As a result, custom audience targeting did not offer a compelling strategy for many mobile app developers. Adding app user IDs as an additional targeting field for custom audiences solves this challenge, allowing developers to request an encrypted ID from Facebook when someone uses their app.

App developers can now reach and reengage their current user base even if they have not registered with the mobile app upon installing it. For example, a retailer can reach and reengage people on Facebook who installed their mobile app and browsed particular products, but who may not have necessarily registered their email address or phone number with the retailer.

Remarket based on specific in-app behavior

Not only can you reengage your mobile user base with app user IDs, you can reengage specific segments depending on their in-app activity – such as if they purchased. Previously marketers could achieve this on Facebook mobile with action-spec targeting if their mobile app leveraged Facebook Login (i.e., via an action defined in Facebook’s Open Graph), and now this can be achieved more seamlessly and without Facebook Login thanks to app user IDs and custom audiences.

Ultimately this means mobile marketers have the opportunity to reach people at the right time with the most relevant messaging possible. For example, as a retailer you may want to message users who have not visited your app in the last two weeks with a different message than someone who just made a purchase.

Privacy friendly, for both consumers and developers

Part of the beauty of this reengagement solution is in the anonymity and privacy it provides to consumers and app developers. No personal information is exchanged between Facebook and developers, nor any third parties advertisers may work with.

A process similar to encryption called hashing is used to create an anonymous fingerprint of data from your app. These hashes are designed to protect against reverse engineering, and no personal information is ever exchanged or revealed. The advertiser’s hashed list is matched with a similarly hashed list of Facebook profile data, with matching hashes aggregated into a targetable audience. This process enables remarketing without personal or identifiable information ever leaving Facebook or the advertiser’s servers, introducing a powerful reengagement solution for the mobile industry.

Benefit from cross platform consistency

Not only can companies with mobile apps now remarket to their user bases with a laser focus with app user IDs, they can do so across devices. For example, as a retailer you may want to reach someone on Facebook desktop who earlier in the day browsed your mobile app and expressed interest in purchasing by adding items to their cart. Or perhaps you want to reach people who have not opened the mobile app in the last month, with consistent messaging (perhaps with unpublished page post ads) across both desktop and mobile.

Thanks to custom audience targeting with app user IDs, marketers can now effectively connect their remarketing and reengagement efforts on mobile to desktop. This offers consumers heightened relevancy and marketers true cross-platform consistency for their messaging.

Ultimately, Facebook has introduced a more powerful and privacy-friendly reengagement solution for the mobile industry with this extension of custom audiences, available currently on iOS and soon on Android. We look forward to helping our customers leverage the solution in full.